Vulcanization process



Patented July 4, 1950 [TED STATES PATENT ---O--FF-l-CE *--VULCANIZATION PROCESS George E. P. Smitln-Jn, Akron; Ohio, assignor 'to .The Firestone'Tire & Rubber Company, Akron,

Ohio, a corporation of Ohio No. Drawing. Application April .9, 1945, .z- Serial No. 587,439

l Claims. 1

This invention relates to new compounds which are accelerators of the vulcanization of rubber. It includes the. new compounds, the process of vulcanizing, and the vulcanized product.

The new compounds are N,Ndialkylene bissulfenamides of the group consisting of the bis- "thiazyl sulfenamides, the bis thiazolinyl sulfenamides, and the bis-thiocarbamyl sulfenamides. The dialkylene amino groups are preferably of the-piperazine type obtained by carrying out the reaction with a piperazine, either an unsubstituted-piperazine or a substituted piperaz'lne, such as methyl piperazine or 2,5-dimethy1 piperazine, etc.

Thenew products which are accelerators are represented by the general formula:

where R is hydrogen or a hydrocarbon radical, X is thiazyl, thiazolinyl or thiocarbamyl, and a: and yzarewhole numbers, usually not greater than about 16 and preferably are 1, 2 or 3. :c and .111 may be the same, as where piperazine or a dialkyl piperazine is used in producing the compounds; or they-.may be difierent, as, for example, .where either of the following is used:

\ NH CH2 cg 1,4-diazocycloheptene or Trimethylene ethylene diamine UH -CH HN N H Imidazolidine The compounds of this invention may be obtained by any usual method of preparing the sulfenamides. The following examples are illustrative:

Example 1 A solution of grams of 2-mercaptobenzothiazole was prepared with 5.5 grams of sodium hydroxide in 100 to 200 cc. of water. The solution of sodium mercaptobenzothiazole was filtered and to it was added 46.4 grams of piperazine hexahydrate. The solution Was diluted somewhat and-while being cooledand stirred,

*N,N-piperazino bis (benzothiazyl sulfenamide) Example 2 .A solution :of' the sodium .salt of Z mercaptQ 4,5-:dimethyl thiazole was prepared from 725 gramsof the mercaptothiazoleand 4.74 grams -.of sodium hydroxide in several hundred cubic .itwere addedrfirst, 50 grams and then-another centimeters ofwater. This was'filtered, and to 50 grams (tota1=100 grams) of piperazine hexahydrate. The solution was cooled and stirred .while l3.15igrams of iodine inaqueous potassium iodide was slowly added. ,A cream-colored, finely divided solid was formed. This melted at to C. On purification a product melting at 153.5 to 154 0. is obtained.

Analysis:

Found; %N=15.4,%S=34.'7. Calculated for N,N-piperazine bis(4,5-dimethy1 thiazyl sulfenamide) :%N=15.2,%S=34.4.

Other accelerators of the invention include:

N,N'-piperazine bis(4-methy1 thiazyl sullenamide) N,N'-2,5-dimethy1 iperazine bis(4-ethyl thiazyl sulfenamide) N,N'-piperazine bis(dimethy1 thiocarbamyl sulfenamide) N,N'piperazine bis(thiazolinyl sulfenamide) N,N-trimethylene ethylene diamine bis(benzothiazyl sulfenamide) N,N'-imidazolidine bis(benzothiazyl sulfenamide) N,N-piperazine bis(benzothiazyl sulfenamide) and N,N-piperazine bis(l,5-dimethyl thiazyl sulfenamide), prepared according to the above two examples, were tested as accelerators of rubber and compared with N-cyclohexyl benzothiazyl 3 sulfenamide as a control, by first compounding them according to the following formula:

Parts by weight Rubber 100 Sulfur 3 Stearic acid 1.10 Zinc oxide 5 Accelerator 0.75

These stocks were cured at different temperatures for difierent periods of time with the following results:

The times of cure are given in minutes immediately below the Modulus and tensile headings in the above tables.

It is seen that these compounds are excellent delayed-action accelerators.

Although the above figures relate to the vulcanization of natural rubber, the invention is not limited to the treatment of that particular material. It includes, also, the curing of synthetic rubber-like materials and other plastics. The examples are merely illustrative of the action of these accelerators on sulfur in any curing operation. Although they relate particularly to the lois-sulfenamides, sulfenamides containing a single sulfur atom connected with a cyclic diamine which also are accelerators may be similarly prepared.

What I claim is:

1. The method of vulcanizing rubber which comprises heating the same to a curing temperature with sulfur in the presence of a small amount of an accelerator which is a sulfenamide of the following formula:

in which R. is from the group consisting of hydrogen and a hydrocarbon radical, X is from the group consisting of thiazyl, thiazolinyl and thincarbamyl, and a: and y are whole numbers.

2. The method of vulcanizing rubber which comprises heating the same to a curing temperature with sulfur in the presence of a small amount of an accelerator which is a N,N-piperazino bissulfenamide of the group consisting of the thiazyl sulfenamides, the thiazolinyl sulfenamides, and the thiocarbamyl sulfenamides.

3. Rubber which has been vulcanized in the presence of an accelerator which is a sulfenamide of the following formula:

in which R is from the group consisting of hydrogen and a hydrocarbon radical, X is from the group consisting of thiazyl, thiazolinyl and thiocarbamyl, and :c and y are whole numbers.

4. Rubber which has been vulcanized in the presence of an accelerator which is a N,N'-piperazino bis-sulfenamide of the group consisting of the thiazyl sulfenamides, the thiazolinyl sulfenamides, and the thiocarbamyl sulfenamides.

GEORGE E. P. SMITH, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,616,994 Sebrell Feb. 8, 1927 1,732,486 Scott Oct, 22, 1929 2,271,834 Carr Feb, 3, 1942 2,345,236 Chitwood Mar. 28, 1944 2,354,427 Carr July 25, 1944 2,382,793 Howland Aug. 14, 1945 

1. THE METHOD OF VULCANIZING RUBBER WHICH COMPRISES HEATING THE SAME TO A CURING TEMPERATURE WITH SULFUR IN THE PRESENCE OF A SMALL AMOUNT OF AN ACCELERATOR WHICH IS A SULFENAMIDE OF THE FOLLOWING FORMULA: 